1. Field of the Invention
The present invention relates to a painting on a surface of a product such as a wheel cower in which a pattern is magnetically formed by using a paint medium containing magnetic bodies. The invention also relates to the painted product, a method of making the painted product, and an apparatus for painting the product.
2. Description of the Background Art
Conventionally, there has been used a metallic painting coated on a surface of a metallic or plastic product in which a metallic luster is obtained on the painted surface by using a transparent paint medium containing fine powders of aluminum or oxidized iron, where the metallic luster is produced by the reflection of the incident light rays in random directions by the fine powders contained within the paint medium.
On the other hand, conventionally, the pattern of desired shape has been formed on a metallic or plastic product by using a mask painting. In such a mask painting, the product manufactured in a desired form is covered by a masking having either a negative or a positive shape corresponding to the desired pattern to be formed and the spray painting is applied onto the masked product.
However, the pattern formed by such a conventional mask painting procedure has a very poor sense of perspective.
For this reason, in order to obtain the sufficient sense of perspective, it has been necessary conventionally to manufacture the product in a three dimensional shape.
However, when the product is formed in a three dimensional shape by using an injection molding, a flow mark or a weld line is easily formed on a surface of the molded product due to the flow of the molding material such as synthetic resin through the injection portion of the mould during the injection molding process, and the mechanical strength of the product is reduced at such a weld line while the outer appearance is damaged at such a flow mark.
In order to cope with this situation, there has been proposed in Japanese Patent Application Laid Open No. 63-175670 a method of forming a pattern by utilizing the magnetic field. In this method, a product to be painted made of a non-magnetic material such as plastic or a ferromagnetic material such as iron is painted with a paint medium containing fine powders of magnetic bodies in a fluid state first, and then a pattern is formed on the painted product by applying the magnetic field to the painted product while the paint medium is still in the fluid state in which the fine powders of the magnetic bodies contained within the paint medium can freely move within the paint medium.
In this method, the pattern is formed within the paint layer on the painted surface by the application of the magnetic field which changes the orientation of the fine powders of the magnetic bodies contained within the paint medium with respect to the painted surface and moves or concentrates the fine powders of the magnetic bodies along the magnetic field lines.
However, this method requires the thickness of the paint layer to be sufficiently greater than the size of the fine powders of the magnetic bodies because it is necessary to move and change the orientation of the magnetic bodies within the paint layer. In addition, it is also necessary in this method to maintain the fluid state of the paint medium until the move and the change of the orientation of the magnetic bodies are completed.
As a consequence, it is difficult for this method to be carried out at high speed because the drying of the paint medium must be slow, and in addition, it is difficult to apply this method to a surface inclined with respect to the horizontal plane.
Moreover, the pattern that can be formed by using this method is rather limited because it is difficult to manipulate the regularity of the orientation of the magnetic bodies locally. In particular, it has been difficult to form a magnet configuration capable of forming a desired pattern having a desired size, a desired contour line width, and a desired contrast with respect to the other portion. In addition, it has been very difficult to change the width of the contour line freely or continuously.
Furthermore, in this method, there is a possibility of leaving line shaped traces on the painted surface due to the magnetic bodies moved within the paint layer, which can damage the outer appearance of the painted product significantly.